(a) Each transmission line valve must be inspected and partially operated at intervals not exceeding 15 months, but at least once each calendar year.

(b) Each operator must take prompt remedial action to correct any valve found inoperable.

(c) The location of all valves in transmission lines shall be designated on appropriate records, drawings or maps in relation to aboveground structures, so that the valves and associated access covers can be readily located when the ground is covered with snow and ice. Since there may be changes or alterations in aboveground structures over a period of time, the accuracy of the reference points established shall be verified at the time of the periodic inspection.

(d) At the time of the periodic inspection, valves will be checked for external leakage.